While there are numerous exercise activities that one may participate in, exercise may be broadly broken into the categories of aerobic exercise and anaerobic exercise. Aerobic exercise generally refers to activities that substantially increase the heart rate and respiration of the exerciser for an extended period of time. This type of exercise is generally directed to enhancing cardiovascular performance. Such exercise usually includes low or moderate resistance to the movement of the individual. For example, aerobic exercise includes activities such as walking, running, jogging, swimming or bicycling for extended distances and extended periods of time.
Anaerobic exercise generally refers to exercise that strengthens skeletal muscles and usually involves the flexing or contraction of targeted muscles through significant exertion during a relatively short period of time and/or through a relatively small number of repetitions. For example, anaerobic exercise includes activities such as weight training, push-ups, sit-ups, pull-ups, or a series of short sprints.
To build skeletal muscle, a muscle group is contracted against resistance. The contraction of some muscle groups produces a pushing motion, while the contraction of other muscle groups produces a pulling motion. A cable machine is a popular piece of exercise equipment for building those muscle groups that produce pulling motions. A cable machine often includes a cable with a handle connected to a first end and a resistance mechanism connected to a second end. Generally, the resistance mechanism is a selectable set of weights. A midsection of the cable is supported with at least one pulley. To move the cable, a user pulls on the handle with a force sufficient to overcome the force of the resistance mechanism. As the cable moves, the pulley or pulleys direct the movement of the cable and carry a portion of the resistance mechanism's load.
One type of cable exercise machine is disclosed in WIPO Patent Publication No. WO/2007/015096 issued to Andrew Loach. In this reference, an exercise apparatus allows the user to perform a variety of aerobic and strength training exercises. A user input means allows the user to apply torque to an input shaft of a resistance unit. A control means adjusts the resistance provided by a resistance means coupled to the input shaft according to the output of a number of sensors. In a preferred embodiment, the resistance unit is able to simulate at the input shaft the dynamic response of a damped flywheel or the dynamic response of an object driven through a viscous medium, or to maintain the resistance at a constant level that is set by the user. The resistance unit includes a battery or an electric generator device and can be operated without connection to an external power source. Other types of cable exercise machines are described in U.S. Patent Publication Nos. 2012/0065034 issued to Andrew Loach and 2006/0148622 issued to Ping Chen.